1. Field of the Invention
The present invention relates generally to wireless local area networking and more particularly to the creation of voice and data priority channels which allows for the effective transfer of voice packets and data frames over a wireless network such that both channels enjoy relative efficiency without suffering degradation with regard to either transfer.
2. The Prior Art
Digital data communications networks are known, consisting of one or more centrally located nodes in communication with multiple distributed remote nodes over spread spectrum full duplex radio frequency links. The purpose of the network system is to transfer user digital data packets between user equipment installations located at the central and remote nodes. This is accomplished by accepting user data packets at the central and remote nodes, encapsulating them within a communications protocol used between the central node and remote nodes over the spread spectrum RF (radio frequency) link, and then returning them to the user equipment at the correct destination. The overall scheme of the network system is shown in FIG. 1.
Referring first to FIG. 1, the environment comprises a digital data communications network, with a central node(s) 10 in communication with a multiplicity of remote nodes 20 over full duplex radio frequency links. The network system transfers user digital data packets between user equipment installations located at the central and remote nodes. User data packets are accepted at the central and remote nodes, having been encapsulated within a communications protocol used between the central and remote nodes over an RF link, and returning the data packets to the user equipment at the correct location.
For the purposes of this invention, data transmission can be roughly grouped into two categories, streamed data and acknowledge-gated data. Streamed data is exemplified by voice and video applications which typically run under the UDP (User Datagram Protocol) sub-protocol of IP (Internet Protocol). In this format, data packets are injected into the IP network at essentially the same rate as they are created. The design requirements for streamed data center primarily around low packet handling times at each IP subsystem along the packet route, since both video and voice are real-time based data systems and induced packet delays along the way can become quite detectable to the user. Packet drop-outs in this mode are a lower priority concern than delay, since the integration capability of the human auditory and visual senses compensates for minor packet drop-outs. The streamed UDP data of voice and video applications usually originate at real-time level sampling devices, making the nature of such transmission small sized packets (in the range of tens to low hundreds of bytes per packet) provided by the IP network at regular and short time intervals (in the range of tens of milliseconds). The major performance factor in this model is the number of packets transferred per second over the RF link, since the packet handling overhead of the protocol far exceeds the processing of the packet-contents.
Acknowledge-gated data is primarily carried by the TCP (Transmission Control Protocol) sub-protocol of IP and is exemplified by such applications as FTP (File Transfer Protocol). In this model, the reservoir of data at the originator is large and non-real time based. Delay in processing data packets along the transmission route is not as critical as in the streamed model, since the data reservoir is fixed and does not change over time. The central design factor in gated transmission is accuracy, rather than latency. The normal gated application carves the data reservoir into relatively large packets (tens of hundred of bytes), sends a small number of such packets to the destination, and then stops transmission until the destination acknowledges reception of those packets. The number of packets sent in a single acknowledged burst is kept small in order to minimize the time required to effect retransmission should the packets not arrive at the destination accurately. The pause in transmission is caused by the half duplex nature of the IP network foundation (ethernet), which prevents the streamed data packet transmission and simultaneous acknowledgement usually found in full duplex protocols (e.g. SNA, Systems Network Architecture). In the data mode model, the relevant performance figure is data transfer rate in kilobits per second, since the packets are large and packet handling overhead small with respect to the processing of the packet contents.
The differences in these two modes of operation make it difficult, if not impossible, to handle both with maximum efficiency and performance at the same time. If one attempts to optimize for small unacknowledged UDP packets, the larger TCP packets must be fractured into small pieces then reassembled at the destination, a philosophy guaranteed to introduce protocol complexity, inefficiency, and larger processor usage. There is no single mode of operation which will optimize both protocol models simultaneously.